1. Field
The present disclosure relates to the field of communications, and in particular to a method and apparatus for measuring a filtering characteristic, pre-equalizer and communication equipment.
2. Description of the Related Art
As the requirements of an optical communication system on low cost, miniature and flexible configuration, optical and electrical bandwidths of a transmitter of the optical communication system are reduced for various reasons. Currently, a problem of narrow bandwidth may be overcome by using pre-equalization, pre-distortion and pre-emphasis technologies in a digital domain.
FIG. 1 is a schematic diagram of a transmitter in the related art using the digital pre-equalization technology. As shown in FIG. 1, the transmitter 100 includes an emitter 101, a pre-equalizer 102, a digital-to-analog converting module 103, a laser 104 and an optical modulator 105, the optical modulator 105 including a pluggable interface, and an electrical driving amplifier, etc.; wherein, the emitter 101 emits digital electrical signals, the pre-equalizer 102 pre-compensates for a filtering damage to the emitted digital electrical signals brought about by subsequent filtering modules of the transmitter 100, such as the digital-to-analog converting module 103 and the optical modulator 105, the compensated digital electrical signals are converted into analog signals after passing through the digital-to-analog converting module 103, and optical signals are outputted after the analog signals are modulated by the optical modulator 105. Here, the filtering damage brought about by the subsequent modules after the pre-equalizer 102 in the transmitter is referred to as a filtering characteristic of a transmitting end.
FIG. 2 is a schematic diagram of a receiver in the related art. As shown in FIG. 2, the receiver 200 includes an optical coherent demodulator 201, a local laser 202, an analog-to digital converting module 203 and a receiving device 204, the optical coherent demodulator consisting of an optical mixer (having no filtering damage) and an optical-to-electrical converter (having filtering damages); wherein, optical signals outputted from the transmitter 100 are demodulated into analog electrical signals by the optical coherent demodulator 201, the analog electrical signals are converted into digital electrical signals by the analog-to digital converting module 203, and the digital electrical signals are received by the receiving device 204. And, a filtering damage exists in the optical signals outputted from the transmitter 100 after passing through the filtering modules of the receiver 200, such as the optical coherent demodulator 201 and the analog-to digital converting module 203. Here, the filtering damage is referred to as a filtering characteristic of a receiving end.
Currently, a common frequency domain or time domain method may be used for pre-equalization, and a coefficient of a pre-equalizer may be obtained by using many methods in the related art, such as zero forcing, and minimum mean square error, etc.; however, a filtering characteristic of a transmitting end needs to be known to these methods.
It should be noted that the above description of the background is merely provided for clear and complete explanation of the present disclosure and for easy understanding by those skilled in the art. And it should not be understood that the above technical solution is known to those skilled in the art as it is described in the background of the present disclosure.